1. Field of the Invention
This invention relates generally to a drive apparatus for tape recorders, and more particularly is directed to an improved drive apparatus for a tape recorder of the type in which the tape is driven in forward and reverse or rewind directions in response to operation of a drive motor in forward and reverse directions, respectively.
2. Description of the Prior Art
It has been proposed to provide a drive apparatus for a cassette tape recorder having its supply and take-up reels bases provided with respective spaced apart selectively driven wheels, in which the drive apparatus comprises a drive wheel located between the driven wheels and being selectively rotated in first and second opposed rotary directions by means of forward and reverse operation of an electric motor, and an idler wheel engaging the drive wheel so as to be rotated thereby and being rotatably carried by a pivotally mounted support arm which is swingable between a first position where the idler wheel bears against one of the driven wheels for driving the latter from the drive wheel and a second position where the idler wheel bears against the other of the driven wheels for driving such other driven wheel from the drive wheel. In the foregoing previously proposed drive apparatus, automatic change-over of the pivotally mounted support arm between its first and second positions is achieved in response to forward and reverse operation of the drive motor by providing a pad of felt or other friction material between the idler wheel and the support arm for frictionally resisting rotation of the idler wheel. The frictional resistance to rotation of the idler wheel by the drive wheel gives rise to a force which urges the pivoted support arm to move in the direction of movement of the drive wheel surface at its line of contact with the idler wheel.
However, the above described pad of felt or other friction material for causing the automatic change-over of the position of the support arm in response to a change in the direction of operation of the drive motor is not wholly reliable in that the frictional characteristic of the felt and the dimensions of the pad or washer formed thereof cannot be maintained precisely uniform, particularly under the requirements of mass production. Therefore, frictional resistance to rotation of the idler wheel relative to its support arm is not uniform and may vary from one drive apparatus to the next or with the passage of time or changes in external conditions. As a result of the foregoing, the load on the drive motor may vary and the reliability of automatic change-over of the tape driving direction is adversely affected, particularly after long periods of operation.